The present invention relates generally to reciprocating compressors, and more particularly to a method and apparatus for direct measurement of rider band wear on a reciprocating compressor.
Industrial reciprocating compressors utilize piston rods and distance pieces to separate the process gas from the oil lubricated components in the frame and crosshead guide. The piston rod moves back and forth and requires support on both ends. On one end of the piston rod, the cross head provides support. An oil pump provides pressurized oil to lubricate the crosshead and crosshead guide.
On the other end, rider bands support the piston assembly and rod. Frequently, the process or process gas cannot tolerate oil or only small amounts of lubrication. With low rates of lubrication, the rider band wears quickly, compared to the lubricated components on the other end of the piston rod. The wear rate may not be linear and can be affected by the quality and quantity of oil in the cylinder, process gas composition, process gas debris and other factors.
To accurately measure the gap between the piston and cylinder bore, the operator must stop the machine, purge the cylinder, remove the cylinder head and/or valve assemblies and use feeler gauges to make the measurement.
Methods currently exist for approximating this measurement. For example, using a sensor mounted at the packing case and geometry to extrapolate wear. Another example is mounting a sensor to the piston and using a wireless apparatus to transmit the gap between the piston and cylinder bore outside of the cylinder to a sensor system. Yet another method involves inferring the gap between the piston and cylinder by measuring the gap between a fixture on the piston and a fixture on the cylinder head. However, these methods all require significant modification of the piston and cylinder head.